1. Field of the Invention
The present invention generally relates to a method and apparatus for transmitting/receiving control information in a wireless communication system. More particularly, the present invention relates to a method and apparatus for transmitting/receiving physical layer control information in a wireless communication system.
2. Description of the Related Art
FIG. 1 illustrates a conventional transmission scheme for a frame including control information in a wireless communication system, especially in a wireless digital broadcasting system.
Referring to FIG. 1, reference numeral 101 denotes one frame. The frame 101 includes a preamble 102, Layer 1 (L1) signaling information 103, Layer 2 (L2) signaling information 104, and at least one Physical Layer Pipe (PLP) 105 to 107. The control information can be delivered in the preamble 102, the L1 signaling information 103, and the L2 signaling information 104, and data is carried in the PLPs 105 to 107.
The preamble 102 is used for time and frequency synchronization and frame synchronization at a receiver. The L1 signaling information 103 is referred to as P2 because it is transmitted in a P2 symbol. P2 represents L1, i.e. physical layer signaling information.
The L1 signaling information 103 includes static, configurable, and dynamic information as indicated by reference numerals 108, 109 and 110, respectively. The static information 108 is almost constant in time, including information about a cell Identifier (ID), a network ID, the number of Radio Frequency (RF) channels, a frame length, and the positions of pilot subcarriers. The configurable information 109 does not change in every frame, but includes information that can be configurable in an upcoming frame. Therefore, the configurable information 109 includes information about a service ID, a modulation scheme, and a code rate used for transmitting service data.
The dynamic information 100 may vary in every frame, including the position of each PLP carrying service data in a current frame, i.e. the start and end of each PLP. In FIG. 1, the L2 signaling information 104 is signaling information about Layer 2 (L2), that is, a Medium Access Control (MAC) layer. A PLP carrying the L2 signaling information 104 is referred to as PLP 0. PLP 0 includes information about the connection between a PLP and a broadcasting service, describing a PLP in which a particular service is received. The PLPs 105 to 107, PLP 1 to PLP N, convey at least one service channel. As the PLPs 105 to 107 carry actual broadcasting data, they are also referred to as data PLPs.
To receive a specific broadcasting service channel, a receiver acquires frame synchronization from the preamble 102 and achieves information about a data transmission scheme and a frame length from P2, that is, the L1 signaling information 103. The receiver then detects PLPs carrying the intended service channel from PLPO, that is, the L2 signaling information 104, and receives broadcasting data in the PLPs.
In the case of control information such as signaling information, it may include a large number of dummy bits during encoding in the wireless communication system. These dummy bits dissipate communication resources. Accordingly, there exists a need for a method for encoding control information to efficiently use communication resources.